1. Field of the Invention
This invention relates to a method and an apparatus for the manufacture of filter plugs which are used for and connected to cigarettes.
More particularly, this invention relates to a method and an apparatus for the manufacture of such filter plugs from a formed filter rod of a material such as cellulose acetate by providing axially spaced pockets in the interior of the rod, depositing particulate material therein and cutting the rod between said deposits to provide individual filter plugs each having cores of particulate material.
2. Description of the Prior Arts
Up to the present time, some methods and apparatuses for the manufacture of such filter plugs mentioned above have been proposed.
In U.S. Pat. No. 3,844,200, filter plugs are manufactured by continuously feeding a fibrous filter material in the axial direction, expanding the filter material to make the cross section thereof to be substantially U-shape, depositing particulate material at constant axial intervals, rolling the filter material in a circular column and wrapping the filter material with suitable wrapping material. The device for depositing particulate material comprises a wheel having pockets arranged on the peripheral edge thereof at predetermined spaces, each pocket having a predetermined volume. The wheel is rotated at a speed corresponding to the travelling speed of the filter material. Each pocket receives particulate material from a hopper when it reaches the uppermost position, and deposits the particulate material on the bottom portion of the U-shaped filter material when it is downwardly directed. According to this known method, the filter material is not adhered between cellulose acetate filaments thereof while the filter material is spreaded in substantially U-shaped cross section. Therefore, if any variations in mechanical conditions are occurred within the filter material before the filter material is fed to the apparatus through a trumpet guide, the density of the filter material may be changed in the axial and transverse direction thereof, the positions of particulate material may be changed with regard to the width of the filter material so that the particulate material is biased in the interior of the filter material, and/or the particulate material may be dropped from cut edges when the filter material is cut to the individual filter plugs.
In U.S. Pat. No. 3,943,832, a plain plate-like filter material is deformed to a substantially U-shaped channel by a special guide means, so that the variations of the density of particulate material in the transverse direction are eliminated. However, there are no provisions for fixing the particulate material being deposited in the channel and spaced in the longitudinal axial direction. The instability of the positions of the particulate material is not solved.
In U.S. Pat. No. 3,884,741 and U.S. Pat. No. 3,957,563, there is provided a means for eliminating the unevenness of the distribution of particulate material in the axial and transverse directions of the filter material. That is to say, the method is characterized by providing a filter rod of filtering material having a longitudinal axis and cutting the rod in the direction of the axis, exposing the interior of the rod, providing pockets at axially spaced intervals in the interior of the rod, depositing particulate material therein and closing and sealing the rod. However, in this U.S. Patent, there are no disclosures concerning methods for supplying the rod-like filter material to a forming machine. A wind up machine for the filter material known in the prior art may be used and a continuous rod-like filter material may be supplied directly to the apparatus for manufacturing filter rods containing particulate material without a last cutting step. In this case, the rod-like filter material must be cut in the axial direction immediately after having been wound. Such a rod-like filter material is not fully adhered between cellulose filaments thereof because a sufficient time has not been passed after the rod-like filter material was plastisized. Therefore, the rod-like filter material may be expanded due to the repelment of the interior cellulose filaments, so that it is difficult to obtain desired pockets in which particulate material is deposited.